Real-world vehicles generally emits noises as they are started up. The noises may come from air-conditioning, engine, motor sounds etc.

To replicate such behaviour in-game, the MTR Mod offers the ability for sounds to be added to the vehicle.

There are currently 2 systems available for the MTR Mod: BVE Sound and Legacy Sound.

The BVE sound system is added from MTR 3.1.0-unofficial-1. It is an adaptation of the sound format used by the game BVE Trainsim and OpenBVE.

Specifically, both BVE4/OpenBVE and BVE5/6 sound format is supported. (Note: Plugin-powered sound effect like BveEx/AtsEX are not supported)

Due to the various tools available online for creating BVE-format Motor Sound, as well as the ability to convert sound format from BVE Trains (For authorized conversion), this is the recommended sound format to get started with for new content.

See Custom BVE Train Sound for tutorial.

The legacy sound is the native sound format for the MTR Mod, available starting from MTR 3.0.0 beta-5-unofficial-8.

It features a 10-20 second sound recording of a particular train, which could be mirrored for both acceleration and deceleration.

How LSS works, visualised.

Motor sounds are split into 0.6-second audio files, and are named speed_0a, then speed_0b, speed_0c, speed_1a, and so on.

There are 3 separate “channels” in LSS (a, b and c), and which channel an audio file falls into depends on the alphabet given at the end of the file name. The order in which the file is played depends on the number specified in the audio file name, starting from 0.

When a train is being defined to have a legacySpeedSoundBaseResource, the mod will look for sounds defined as (directory_name)_acceleration_xx in sounds.json.

When a legacyDoorSoundBaseResource is defined, MTR will always try and find a sound named (id)_door_open and (id)_door_close for door open/close sound. They will be played when doors are opening or closing.

Property legacyDoorCloseSoundTime is used to determine when the door sound should be played. If set to 0.5, the sound will be played when the doors start to move. If set to 1, the sound will be played 1-2 seconds before the doors start moving. if the time between doors opening and closing are too short, the game will skip playing door closing sounds completely.